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Boundary layer flow of Maxwell fluid due to torsional motion of cylinder: modeling and simulation

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Applied Mathematics and Mechanics(English Edition) 2020年第4期41卷 667-680页

作者： M.KHAN A.ahmed j.ahmed Department of Mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

This paper investigates the boundary layer flow of the Maxwell fluid around a stretchable horizontal rotating cylinder under the influence of a transverse magnetic *** constitutive flow equations for the current physical problem are modeled and analyzed for the first time in the *** torsional motion of the cylinder is considered with the constant azimuthal velocity *** partial differential equations(PDEs)governing the torsional motion of the Maxwell fluid together with energy transport are simplified with the boundary layer *** current analysis is valid only for a certain range of the positive Reynolds ***,for very large Reynolds numbers,the flow becomes ***,the governing similarity equations are simplified through suitable transformations for the analysis of the large Reynolds *** numerical simulations for the flow,heat,and mass transport phenomena are carried out in view of the bvp4c scheme in *** outcomes reveal that the velocity decays exponentially faster and reduces for higher values of the Reynolds numbers and the flow penetrates shallower into the free stream *** is also noted that the phenomenon of stress relaxation,described by the Deborah number,causes to decline the flow fields and enhance the thermal and solutal energy transport during the fluid *** penetration depth decreases for the transport of heat and mass in the fluid with the higher Reynolds *** excellent validation of the numerical results is assured through tabular data with the existing literature.

关键词： torsional motion Maxwell fluid magnetic field stretchable rotating cylinder bvp4c scheme

Transient flow of magnetized Maxwell nanofluid: Buongiorno model perspective of Cattaneo-Christov theory

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Applied Mathematics and Mechanics(English Edition) 2020年第4期41卷 655-666页

作者： M.KHAN A.ahmed j.ahmed Department of Mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

The present research article is devoted to studying the characteristics of Cattaneo-Christov heat and mass fluxes in the Maxwell nanofluid flow caused by a stretching sheet with the magnetic field *** Maxwell nanofluid is investigated with the impact of the Lorentz force to examine the consequence of a magnetic field on the flow characteristics and the transport of *** heat and mass transport mechanisms in the current physical model are analyzed with the modified versions of Fourier’s and Fick’s laws,***,the well-known Buongiorno model for the nanofluids is first introduced together with the Cattaneo-Christov heat and mass fluxes during the transient motion of the Maxwell *** governing partial differential equations(PDEs)for the flow and energy transport phenomena are obtained by using the Maxwell model and the Cattaneo-Christov theory in addition to the laws of *** transformations are used to convert the PDEs into a system of nonlinear ordinary differential equations(ODEs).The homotopic solution methodology is applied to the nonlinear differential system for an analytic *** results for the time relaxation parameter in the flow,thermal energy,and mass transport equations are discussed *** is noted that higher values of the thermal and solutal relaxation time parameters in the Cattaneo-Christov heat and mass fluxes decline the thermal and concentration fields of the ***,larger values of the thermophoretic force enhance the heat and mass transport in the ***,the Brownian motion of the nanoparticles declines the concentration field and increases the temperature *** validation of the results is assured with the help of numerical tabular data for the surface velocity gradient.

关键词： transient flow Cattaneo-Christov theory Maxwell nanofluid Buongiorno model homotopy analysis method (HAM) solution

Thermal analysis in swirl motion of Maxwell nanofluid over a rotating circular cylinder

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Applied Mathematics and Mechanics(English Edition) 2020年第9期41卷 1417-1430页

作者： A.ahmed M.KHAN j.ahmed Department of Mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

In this paper,the mechanism of thermal energy transport in swirling flow of the Maxwell nanofluid induced by a stretchable rotating cylinder is *** rotation of the cylinder is kept constant in order to avoid the induced axially secondary ***,the novel features of heat generation/absorption,thermal radiation,and joule heating are studied to control the rate of heat *** effects of Brownian and thermophoretic forces exerted by the Maxwell nanofluid to the transport of thermal energy are investigated by utilizing an effective model for the nanofluid proposed by *** whole physical problem of fluid flow and thermal energy transport is modelled in the form of partial differential equations(PDEs)and transformed into nonlinear ordinary differential equations(ODEs)with the help of the suitable flow *** acquired results through the technique bvp4c are reported graphically with physical *** analysis reveals that there is higher transport of heat energy in the Maxwell nanoliquid for a constant wall temperature(CWT)as compared with the prescribed surface temperature(PST).Both thermophoretic and Brownian forces enhance the thermal energy transport in the flowing Maxwell ***,the temperature distribution increases with increasing values of the radiation parameter and the Eckert *** is also noted that an increase in Reynolds number reduces the penetration depth,and as a result the flow and transport of energy occur only near the surface of the cylinder.

关键词： Maxwell nanofluid rotating cylinder heat source/sink joule heating convective condition numerical solution

Fever assessment in children under five: Are we following the guidelines?

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World journal of Clinical Pediatrics 2024年第1期13卷 62-72页

作者： Hasan M Isa ahmed j Isa Murtadha A Alnasheet Mahmood M Mansoor Department of Pediatrics Salmaniya Medical ComplexManama 26671Bahrain Department of Pediatrics Arabian Gulf UniversityManama 26671Bahrain Department of General Surgery Salmaniya Medical ComplexManama 26671Bahrain

BACKGROUND Fever is a common cause of medical consultation and hospital admission,particularly among ***,the United Kingdom’s National Institute for Health and Care Excellence(NICE)updated its guidelines for assessing fever in children under five years of *** efficient assessment and management of children with fever are crucial for improving patient *** To evaluate fever assessment in hospitalized children and to assess its adherence with the NICE Fever in under 5s *** We conducted a retrospective cohort review of the electronic medical records of children under five years of age at the Department of Pediatrics,Salmaniya Medical Complex,Bahrain,between june and july *** data,vital signs during the first 48 h of admission,route of temperature measurement,and indications for admission were *** was defined according to the NICE *** children were divided into five groups according to their age(0-3 months,>3-6 months,>6-12 months,>12-36 months,and>36-60 months).Patients with and without fever were compared in terms of demography,indication for admission,route of temperature measurement,and other vital *** with the NICE Fever in the under 5s guideline was *** compliance was defined as>95%,partial compliance as 70%-95%,and minimal compliance as≤69%.Pearson’sχ^(2),Student’s t test,the Mann-Whitney U test,and Spearman’s correlation coefficient(rs)were used for *** Of the 136 patients reviewed,80(58.8%)were *** median age at admission was 14.2[interquartile range(IQR):1.7-44.4]months,with the most common age group being 36-60 ***-six(26.4%)patients had fever,and 100(73.6%)were *** commonest age group for febrile patients(>12-36 months)was older than the commonest age group for afebrile patients(0-3 months)(P=0.027).The median weight was 8.3(IQR:4.0-13.3)*** with fever had higher weight than those without fever[10.2(IQR:7.3-13.0)vs 7

关键词： Fever Pediatrics Admission patterns Temperature measurement Guidelines Bahrain

Evaluating mechanism of banana pseudo-stem retting using seawater:A cost-effective surface pre-treatment approach

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journal of Bioresources and Bioproducts 2024年第3期9卷 322-335页

作者： Prince Hotor ahmed H.Hassanin Osbert Akatwijuka Mohamed A.H.Gepreel Mitsuo Yamamoto Yukie Saito ahmed Abdel-Mawgood Egypt-japan University of Science and Technology Biotechnology ProgramAlexandria GovernorateNew Borg Al Arab 21934Egypt Alexandria University Department of Textile EngineeringAlexandria GovernorateBab Sharqi 5424041Egypt Egypt-japan University of Science and Technology Material Science and EngineeringAlexandria GovernorateNew Borg Al Arab 21934Egypt Graduate School of Agricultural and Life Sciences The University of TokyoBunkyo-KuTokyo 113-8657Japan

Retting has been employed to extract natural fibers from agricultural wastes as a biological and cost-effective approach for *** its global abundance,banana pseudo-stem is a promising agro-waste for lignocellulosic fiber *** this study,fibers were extracted from the pseudo-stems after being pre-treated under four conditions using seawater at room temperature for up to 35 d Bacterial isolation from the fresh seawater sample and screening for ligninolytic ability were *** load as well as laccase and manganese peroxidase enzyme activity profile assay during the retting duration were *** transform infrared(FT-IR)and X-day diffraction(XRD)analyses were also examined for both pre-treated and untreated extracted *** results shows that six out of the eight bacterial isolates had the ability to degrade *** treatments(Raw stem+Raw seawater)and(Autoclaved stem+Raw seawater)recorded the highest viable bacterial load of 9.24×102 and 4.46×102 CFU,respectively,on the 14th day of the retting ***,the highest laccase and manganese peroxidase enzymes activity was recorded for(Raw stem+Raw seawater)and(Autoclaved stem+Raw seawater)treatments in the second to the third *** FT-IR spectra of the pre-treated fibers revealed relative reductions in peaks attributed to polysaccharides and other amorphous substances for all retting *** XRD diffractogram revealed that the crystallinity index(CI)of pre-treated fibers increased in all seawater retting treatment ***,the CI for fibers pre-treated under enzymatic conditions were enhanced even after five *** analysis for selected bacterial isolates showed homology to sequences of Bacillus velezensis,Shewanella sp.L8–5,and Citrobacter amalonaticus and Bacillus subtilis j8 *** these findings,it was suggested that physical,biological,and chemical actions were collectively involved in the seawater retting process of banana ps

关键词： Seawater retting Banana pseudo-stem Natural fiber Enzyme activity Colony forming unit

Pregnancy stressors and postpartum symptoms of depression and anxiety:the moderating role of a cognitivebehavioural therapy(CBT)intervention

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General Psychiatry 2024年第1期37卷 112-121页

作者： Yunxiang Sun Soim Park Abid Malik Najia Atif ahmed Zaidi Atif Rahman Pamela j Surkan Department of International Health Johns Hopkins University Bloomberg School of Public HealthBaltimoreMarylandUSA Department of Public Mental Health Health Services AcademyIslamabadPakistan Human Development Research Foundation RawalpindiPakistan Department of Primary Care and Mental Health Institute of Population HealthUniversity of LiverpoolLiverpoolUK

Background Little is known about the association between stressors(especially positive stressors)during pregnancy and postpartum depression and *** We investigated the association between positive and negative stress events during different stages of pregnancy and postpartum mental health outcomes among low-income pregnant women with symptoms of anxiety in Pakistan and evaluated whether an intervention based on cognitive behavioural therapy(CBT)had a regulatory *** Participants were 621 pregnant Pakistani women with mild *** the Pregnancy Experience Scale-Brief Version,six scores were created to assess positive and negative *** performed a multivariate linear regression to examine whether these six scores,measured both at baseline and in the third trimester,were associated with postpartum anxiety and depressive *** effect of the intervention on this relationship was examined by adding an interaction term to the regression *** Hassles frequency measured in the third trimester was positively associated with depression(B=0.22,95%confidence interval(Cl):0.09 to 0.36)and anxiety(B=0.19,95%Cl:0.08to 0.30).At the same timepoint,uplifts intensity was negatively associated with symptoms of depression(B=-0.82,95%Cl:1.46 to-0.18)and anxiety(B=-0.70,95%Cl:-1.25 to-0.15),whereas hassles intensity was positively related to symptoms of depression(B=1.02,95%Cl:0.36 to 1.67)and anxiety(B=0.90,95%Cl:0.34 to 1.47).The intensity ratio of hassles to uplifts reported in the third trimester was positively related to both depression(B=1.40,95%Cl:0.59 to 2.20)and anxiety(B=1.26,95%Cl:0.57 to 1.96).The intervention strengthened the overall positive effects of uplfts and the negative effects of *** experiences at baseline during early pregnancy to mid-pregnancy were not associated with mental health *** Stressors in the third trimester but not earlier in pregnancy were associated with postpartum symptoms

关键词： postpartum stress behaviour

Rotational flow of Oldroyd-B nanofluid subject to Cattaneo-Christov double diffusion theory

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Applied Mathematics and Mechanics(English Edition) 2020年第7期41卷 1083-1094页

作者： A.HAFEEZ M.KHAN A.ahmed j.ahmed Department of Mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

A nanofluid is composed of a base fluid component and nanoparticles, in which the nanoparticles are dispersed in the base fluid. The addition of nanoparticles into a base fluid can remarkably improve the thermal conductivity of the nanofluid, and such an increment of thermal conductivity can play an important role in improving the heat transfer rate of the base fluid. Further, the dynamics of non-Newtonian fluids along with nanoparticles is quite interesting with numerous industrial applications. The present predominately predictive modeling studies the flow of the viscoelastic Oldroyd-B fluid over a rotating disk in the presence of nanoparticles. A progressive amendment in the heat and concentration equations is made by exploiting the Cattaneo-Christov heat and mass flux expressions. The characteristic of the Lorentz force due to the magnetic field applied normal to the disk is studied. The Buongiorno model together with the Cattaneo-Christov theory is implemented in the Oldroyd-B nanofluid flow to investigate the heat and mass transport mechanism. This theory predicts the characteristics of the fluid thermal and solutal relaxation time on the boundary layer flow. The von K′arm′an similarity functions are utilized to convert the partial differential equations(PDEs) into ordinary differential equations(ODEs). A homotopic approach for obtaining the analytical solutions to the governing nonlinear problem is carried out. The graphical results are obtained for the velocity field, temperature, and concentration distributions. Comparisons are made for a limiting case between the numerical and analytical solutions, and the results are found in good agreement. The results reveal that the thermal and solutal relaxation time parameters diminish the temperature and concentration distributions, respectively. The axial flow decreases in the downward direction for higher values of the retardation time parameter. The impact of the thermophoresis parameter boosts the temperature di

关键词： Oldroyd-B nanofluid rotating disk magnetohydrodynamic(MHD) Cattaneo-Christov theory analytical solution

Von Kármán rotating flow of Maxwell nanofluids featuring the Cattaneo-Christov theory with a Buongiorno model

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Applied Mathematics and Mechanics(English Edition) 2020年第8期41卷 1195-1208页

作者： A.ahmed M.KHAN j.ahmed A.HAFEEZ Department of Mathematics Quaid-i-Azam UniversityIslamabad 44000Pakistan Department of Basic Sciences University of Engineering and TechnologyTaxila 47050Pakistan

This research paper analyzes the transport of thermal and solutal energy in the Maxwell nanofluid flow induced above the disk which is rotating with a constant angular *** significant features of thermal and solutal relaxation times of fluids are studied with a Cattaneo-Christov double diffusion theory rather than the classical Fourier’s and Fick’s laws.A novel idea of a Buongiorno nanofluid model together with the Cattaneo-Christov theory is introduced for the first time for the Maxwell fluid flow over a rotating ***,the thermal and solutal distributions are controlled with the impacts of heat source and chemical *** classical von Karman similarities are used to acquire the non-linear system of ordinary differential equations(ODEs).The analytical series solution to the governing ODEs is obtained with the well-known homotopy analysis method(HAM).The validation of results is provided with the published results by the comparison *** graphically presented outcomes for the physical problem reveal that the higher values of the stretching strength parameter enhance the radial velocity and decline the circumferential *** increasing trend is noted for the axial velocity profile in the downward direction with the higher values of the stretching strength *** higher values of the relaxation time parameters in the Cattaneo-Christov theory decrease the thermal and solutal energy transport in the flow of Maxwell *** higher rate of the heat transport is observed in the case of a larger thermophoretic force.

关键词： Maxwell fluid nanoparticle Cattaneo-Christov theory rotating disk homotopy analysis method(HAM)

A Novel Layered Double Hydroxide and Dodecyl Alcohol Assisted PCM Composite with High Latent Heat Storage Capacity and Thermal Conductivity

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journal of Thermal Science 2024年第2期33卷 537-547页

作者： AL-ahmed Amir SARI Ahmet KHAN Firoz AL-RASHEIDI Masoud Hekimoğlu Gökhan AFZAAL Mohammad A.ALSULAMI ahmed DAFALLA Hatim SALHI Billel A.ALSULAIMAN Fahad Interdisciplinary Research Center for Renewable Energy and Power Systems(IRC-REPS) King Fahd University of Petroleum&MineralsDhahran31261Saudi Arabia Department of Metallurgical and Material Engineering Karadeniz Technical UniversityTrabzon61080Turkey Maths and Natural Sciences Division Higher Colleges of TechnologyP.O.Box 7947SharjahUnited Arab Emirates Department of Mechanical Engineering King Fahd University of Petroleum&MineralsDhahran31261Saudi Arabia Core Research Facilities King Fahd University of Petroleum&MineralsDhahran31261Saudi Arabia Interdisciplinary Research Center for Membranes and Water Security King Fahd University of Petroleum&MineralsDhahran31261Saudi Arabia

Dodecyl alcohol(DDA) is a promising solid-liquid phase change material(PCM) due to its favorable latent heat storage(LHS) ***,the leakage issue of PCM in a melted state during the heating period and low thermal conductivity restricts its utilization potential in thermal energy storage(TES) *** the same context,the present work aims to overcome the leakage issue and improve the thermal conductivity of the *** this in mind,a novel leak-proof layered double hydroxide(LDH)/DDA composite PCM is proposed through a solution-based impregnation *** leak-proof impregnation ratio of the DDA impregnated within the cavities of the synthesized Al/Fe-LDH was determined to be 60%.Detailed morphological,physicochemical,and thermal properties of the fabricated composite were studied by scanning electron microscopy(SEM),Fourier transforms infrared(FTIR) spectroscopy,X-ray diffraction(XRD)spectroscopy,differential scanning calorimetry(DSC),thermalgravimetric analysis(TGA),and thermal cycling *** results show that the LDH/DDA composite has a suitable phase change temperature(about 20℃) for passive solar thermal management of building *** composite PCM showed high LHS enthalpy(about136 j/g),good thermal stability,and cycling LHS *** also showed nearly 152% higher thermal conductivity compared to that of pure DDA,ultimately reducing the melting and solidification time of the pure DDA by 44.9% and 45.5%,respectively.

关键词： dodecyl alcohol layered double hydroxide composite PCM thermal conductivity thermal energy storage(TES)